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What causes schizophrenia?

There is no known single cause of schizophrenia. Much is still unknown about the brain and what it does. Schizophrenia is probably caused by problems with brain functioning and triggered by stress.

How does the brain work?

The brain works by using special chemicals called neurotransmitters. When a person develops schizophrenia, it seems that these chemicals in the brain are affected. This chemical change can occur at times in people's lives when they are experiencing a great deal of stress. People with schizophrenia have a different chemical makeup of the brain than people who do not have it.

Possible causes of schizophrenia

1. Genetics

Schizophrenia tends to run in families. This does not mean that if a relative has schizophrenia, you will get it. But it does mean that there is a greater chance of getting schizophrenia.

2. Chemical imbalance in the brain

Scientists believe that over activity of certain chemicals in the brain may cause schizophrenia. Neurotransmitters, chemicals that allow communication between nerve cells, have long been thought to be involved in the development of schizophrenia. The neurotransmitters dopamine and glutamate may be involved.

3. Different brain structure

Many studies of people with schizophrenia have found that some brain structures might be different. Some parts of the brain might be bigger and some might be smaller when compared to people who do not have schizophrenia. Not all people with schizophrenia have different brain structures.

Many studies of people with schizophrenia have found physical abnormalities in the brain structure of people who have the illness. For example, enlargement of the fluid-filled cavities, called the ventricles, in the interior of the brain, and decreased size of certain brain regions. The have also found abnormalities, such as decreased metabolic activity in certain brain regions.

Not all people with schizophrenia have these physical abnormalities. Microscopic studies of brain tissue after death have also shown small changes in the distribution or number of brain cells in people with schizophrenia. It appears that many (but probably not all) of these changes are present before an individual becomes ill, and schizophrenia may be, in part, an illness resulting from adnormal in development of the brain.

Scientists have found that schizophrenia may be a developmental disorder resulting when neurons form inappropriate connections during fetal development. These errors may lie inactive until puberty, when changes in the brain that occur  normally during this critical stage of maturation interact adversely with the faulty connections.

4. Pregnancy complications

Studies show that damage to the brain at or before birth can cause schizophrenia.

5. Stress

Everyone has stress. Stress does not cause schizophrenia. But a stressful event can play a part in causing someone to get sick for the first time, or to get sick again.

6. Drug use

Some studies show that the use of illegal street drugs, such as LSD, has played a role in triggering the onset of schizophrenia.

What does not cause schizophrenia?

We do know that bad parenting, trauma, abuse or personal weakness does not cause schizophrenia. Families do not cause schizophrenia.

What do scientists know about schizophrenia?

Scientists are studying genetic factors in schizophrenia.  Some believe that multiple genes are involved in creating a tendency to get schizophrenia.  However, it is not yet understood exactly how genetics play a role, and it cannot be predicted whether a given person will or will not develop the disorder.  In addition, events such as pregnancy difficulties like intrauterine starvation, viral infections, or other obstruction complications seem to influence the development of schizophrenia.

In order to learn more about the genetic basis for schizophrenia, the National Institute of Mental Health has established a Schizophrenia Genetics Initiative that is gathering data from a large number of families of people with the illness. 

Schizophrenia studies

In other studies, investigators using brain-imaging techniques have found evidence of early biochemical changes that may precede the onset of disease symptoms, prompting examination of the neural circuits that are most likely to be involved in producing those symptoms.  Meanwhile, scientists working at the molecular level are exploring the genetic basis for abnormalities in brain development and in the neurotransmitter systems regulating brain function.

No one knows for sure what causes schizophrenia.  Much of the scientific research has been focused on genetics, the role of stress, the role of the family and environmental factors in the development of schizophrenia.  Currently, there is no evidence to suggest that only one factor causes schizophrenia, but rather many factors play a role.